An experimental approach to quantify strain transfer efficiency of fibre bragg grating sensors to host structures

This paper developed a method to evaluate the strain transfer efficiency of fibre Bragg grating sensors to host structures. Various coatings were applied to fibre Bragg grating sensors after being fabricated. They were epoxy, silane agent and polypropylene, representing different surface properties. A neat epoxy resin plate was used as the host in which the coated fibre sensors were embedded in the central layer. The tensile strain output from the FBGs was compared with that obtained from electrical strain gauges which were attached on the surface of the specimen. A calculating method based on the measured strains was developed to quantify the strain transfer function of different surface coatings. The strain transfer coefficient obtained from the proposed method provided a direct indicator to evaluate the strain transfer efficiency of different coatings used on the FBG sensors, under either short or long-term loading. The results demonstrated that the fibre sensor without any coating possessed the best strain transfer, whereas, the worst strain transfer was created by polypropylene coating. Coatings play a most influential role in strain measurements using FBG sensors

50 years of British accent bias

Do accent biases observed half a century ago (Giles 1970) and 15 years ago (Coupland & Bishop 2007) still hold today in Britain? We provide an updated picture of national attitudes to accent labels by replicating and extending previous studies. Mean ratings and relative rankings of 38 accents for prestige and pleasantness by a large representative sample of the British population (N = 821) attest to a remarkably stable, long-standing hierarchy of accent status. We find little evidence of demotion of conservative prestige varieties or reranking of accents, although we do observe a slight improvement in lower rankings. We focus in detail on age and life stage, finding that most of the age patterns observed in earlier studies were in fact instances of age-grading (lifespan effects), not real-time change in attitude. The midlife phase of life corresponds to conservative shifts in the perception of global, migrant-heritage, and stigmatised varieties. Our findings add change in speech evaluation to the growing body of research on lifespan change in speech production. Finally, although effects of ethnicity, social class, regional self- and other-bias, and age remain firmly in place, earlier gender differences in respondent behaviour have more or less disappeared

Realizing Hopf Insulators in Dipolar Spin Systems

The Hopf insulator represents a topological state of matter that exists outside the conventional ten-fold way classification of topological insulators. Its topology is protected by a linking number invariant, which arises from the unique topology of knots in three dimensions. We predict that three-dimensional arrays of driven, dipolar-interacting spins are a natural platform to experimentally realize the Hopf insulator. In particular, we demonstrate that certain terms within the dipolar interaction elegantly generate the requisite non-trivial topology, and that Floquet engineering can be used to optimize dipolar Hopf insulators with large gaps. Moreover, we show that the Hopf insulator's unconventional topology gives rise to a rich spectrum of edge mode behaviors, which can be directly probed in experiments. Finally, we present a detailed blueprint for realizing the Hopf insulator in lattice-trapped ultracold dipolar molecules; focusing on the example of ${}^{40}$K$^{87}$Rb, we provide quantitative evidence for near-term experimental feasibility.Comment: 6 + 7 pages, 3 figure

A potential mechanism for targeting aggregates with proteasomes and disaggregases in liquid droplets

Insoluble protein deposits are hallmarks of neurodegenerative disorders and common forms of dementia. The aberrant aggregation of misfolded proteins involves a complex cascade of events that occur over time, from the cellular to the clinical phase of neurodegeneration. Declining neuronal health through increased cell stress and loss of protein homeostasis (proteostasis) functions correlate with the accumulation of aggregates. On the cellular level, increasing evidence supports that misfolded proteins may undergo liquid-liquid phase separation (LLPS), which is emerging as an important process to drive protein aggregation. Studying the reverse process of aggregate disassembly and degradation has only recently gained momentum, following reports of enzymes with distinct aggregate-disassembly activities. In this review, we will discuss how the ubiquitin-proteasome system and disaggregation machineries such as VCP/p97 and HSP70 system may disassemble and/or degrade protein aggregates. In addition to their canonically associated functions, these enzymes appear to share a common feature: reversibly assembling into liquid droplets in an LLPS-driven manner. We review the role of LLPS in enhancing the disassembly of aggregates through locally increasing the concentration of these enzymes and their co-proteins together within droplet structures. We propose that such activity may be achieved through the concerted actions of disaggregase machineries, the ubiquitin-proteasome system and their co-proteins, all of which are condensed within transient aggregate-associated droplets (TAADs), ultimately resulting in aggregate clearance. We further speculate that sustained engagement of these enzymatic activities within TAADs will be detrimental to normal cellular functions, where these activities are required. The possibility of facilitating endogenous disaggregation and degradation activities within TAADs potentially represents a novel target for therapeutic intervention to restore protein homeostasis at the early stages of neurodegeneration

50 years of British accent bias: Stability and lifespan change in attitudes to accents

Do accent biases observed half a century ago (Giles 1970) and 15 years ago (Coupland and Bishop 2007) still hold in Britain today? We provide an updated picture of national attitudes to accent labels by replicating and extending previous studies. Mean ratings and relative rankings of 38 accents for prestige and pleasantness by a large representative sample of the British population (N = 821) attest to a remarkably stable, long-standing hierarchy of accent status. We find little evidence of demotion of conservative prestige varieties or reranking of accents, although we do observe a slight improvement in lower rankings. We focus in detail on age and life stage, finding that most of the age patterns observed in earlier studies were in fact instances of age-grading (lifespan effects), not real-time change in attitude. The midlife phase of life corresponds to conservative shifts in the perception of global, migrant-heritage, and stigmatised varieties. Our findings add change in speech evaluation to the growing body of research on lifespan change in speech production. Finally, although effects of ethnicity, social class, regional self- and other-bias, and age remain firmly in place, earlier gender differences in respondent behaviour have more or less disappeared

Surface Scattering via Bulk Continuum States in the 3D Topological Insulator Bi2_{2}Se3_{3}

We have performed scanning tunneling microscopy and differential tunneling conductance ($dI/dV$) mapping for the surface of the three dimensional topological insulator Bi$_{2}$Se$_{3}$. The fast Fourier transformation applied to the $dI/dV$ image shows an electron interference pattern near Dirac node despite the general belief that the backscattering is well suppressed in the bulk energy gap region. The comparison of the present experimental result with theoretical surface and bulk band structures shows that the electron interference occurs through the scattering between the surface states near the Dirac node and the bulk continuum states.Comment: 5 pages, 4 figure

Structural phase transition and dielectric relaxation in Pb(Zn1/3Nb2/3)O3 single crystals

The structure and the dielectric properties of Pb(Zn1/3Nb2/3)O3 (PZN) crystal have been investigated by means of high-resolution synchrotron x-ray diffraction (with an x-ray energy of 32 keV) and dielectric spectroscopy (in the frequency range of 100 Hz - 1 MHz). At high temperatures, the PZN crystal exhibits a cubic symmetry and polar nanoregions inherent to relaxor ferroelectrics are present, as evidenced by the single (222) Bragg peak and by the noticeable tails at the basis of the peak. At low temperatures, in addition to the well-known rhombohedral phase, another low-symmetry, probably ferroelectric, phase is found. The two phases coexist in the form of mesoscopic domains. The para- to ferroelectric phase transition is diffused and observed between 325 and 390 K, where the concentration of the low-temperature phases gradually increases and the cubic phase disappears upon cooling. However, no dielectric anomalies can be detected in the temperature range of diffuse phase transition. The temperature dependence of the dielectric constant show the maximum at higher temperature (Tm = 417 - 429 K, depending on frequency) with the typical relaxor dispersion at T < Tm and the frequency dependence of Tm fitted to the Vogel-Fulcher relation. Application of an electric field upon cooling from the cubic phase or poling the crystal in the ferroelectric phase gives rise to a sharp anomaly of the dielectric constant at T 390 K and diminishes greatly the dispersion at lower temperatures, but the dielectric relaxation process around Tm remains qualitatively unchanged. The results are discussed in the framework of the present models of relaxors and in comparison with the prototypical relaxor ferroelectric Pb(Mg1/3Nb2/3)O3.Comment: PDF file, 13 pages, 6 figures collected on pp.12-1